Known from the state of the art are temperature sensors for industrial process technology. Their construction is similar to that of thermal, flow measuring devices, with the difference that conventional thermal, flow measuring devices usually use two temperature sensors, which are embodied as equally as possible and arranged in, most often, pin-shaped, metal sleeves, so-called stingers or prongs, and which are in thermal contact with the medium flowing through a measuring tube or through a pipeline. Most often, they are immersed in the medium. For industrial application, the two temperature sensors are usually installed in a measuring tube; the temperature sensors can, however, also be directly mounted in the pipeline. One of the two temperature sensors is a so-called active temperature sensor, which is heated by means of a heating unit. Provided as a heating unit is either a separate resistance heater or the temperature sensor itself is a resistance element, e.g. an RTD (Resistance Temperature Device) sensor, which is heated by I2R heating, e.g. by a corresponding variation of the measuring current. The second temperature sensor is a so-called passive temperature sensor and measures the temperature of the medium at as small as possible self-warming by the measurement current.
Until now, mainly RTD-elements with helically wound, platinum wires have been applied in thermal, flow measuring devices. In the case of thin film, resistance thermometers (TF-RTDs), conventionally, a meander-shaped platinum layer is vapor deposited on a substrate. In addition, a glass layer is applied for protection of the platinum layer. The cross section of the thin film, resistance thermometer is rectangular, in contrast with the round cross section of RTD-elements. Heat transfer into the resistance element and/or from the resistance element occurs accordingly via two oppositely lying surfaces, which together make up a large part of the total surface of a thin film, resistance thermometer.